Syria is controlled by the Assad family, part of the minority Alawite population. They are a sect of Shia Islam, which is why they are supported by Iran. Iran is also paying Hezbollah, which is made up of Shia Lebanese, to fight in support of the Assad regime. The vast majority of the Syrian population, including the Kurds, are Sunni. Nothing would make the Assad regime happier than for its Sunni majority population to flee, and they are encouraging them to do so.
Iraq is just as hosed up. Once we displaced Saddam and his minority Sunni regime, the majority Shia population came to dominate the government. With us (U.S.) no longer there to keep a lid on things (nice move Barry), the majority Shia sought retribution for their long suffering under Sunni rule. The now persecuted Sunnis figured they had ruled the Shia before, and could surely do so again - and thus began ISIS, complete with former Saddam regime military officers in its upper ranks. Meanwhile, the moderate Kurds in the north just want to be left alone - except for the PKK who like to piss off the Turks - who are currently dismantling the secular state created be Mustafa Kermal Ataturk, and heading off into Islamic field....
Lebanon is made up of Christians, Shia and Sunnis. Yemen is Shia and Sunni, with tribal elements thrown in just for fun. This whole area is just one balkanized mess. During WWI, two idiots, one French (Georges-Picot) and the other British (Sykes), both with immaculate credentials, divided up the former Ottoman Empire among themselves (with a few bones thrown to the Arabs) with very little consideration for facts on the ground - like who lived where. We're still paying for their ineptitude.
Present day Syria, Iraq and Yemen are failed states that should have never been, meanwhile the Kurds are scattered through parts of Iraq, Iran, Syria and Turkey. The best thing we could do at this point is to draw some new lines that actually take reality into consideration. Then maybe they could stay where they are. Or we could just nuke the place. The again, if we'd just close up the borders, but otherwise get out of the way, they'd continue to self exterminate...
Enough fun for one night, I have some work to do. MSG